[eluser]Derek Allard[/eluser]
If I give reasons then everyone is going to argue them with me... I don't really want that.
The short version is that we feel the additional comments made the code harder to read by a human, and increase the codebase by (6200 variable declarations x 3 lines) over 18,000 additional lines that while useful for some people are not useful for all.
Now please, please, please don't take this as a condemnation of phpdoc or us not wanting to support it or anything like that. It is not. The truth is, its a stylistic preference for right now, and if it changes in the future I hope that you'll still be around to give us a hand.